The present disclosure relates to optical surgery, and more specifically to surgical replacement of a patient's lens.
The human eye, in simple terms, functions to provide vision by transmitting and refracting light through a clear outer portion called the cornea and focusing the image by way of the lens onto the retina at the back of the eye. The quality of the focused image depends on many factors including the size, shape, and length of the eye, and the shape and transparency of the cornea and lens.
When trauma, age, or disease causes the lens to become less transparent, vision deteriorates because of a reduction in light transmitted to the retina. This deficiency in the eye's lens is medically known as a cataract. The treatment for this condition is often surgical removal of the lens and implantation of an artificial lens, typically termed an intraocular lens (IOL).
An IOL is often foldable and inserted into the eye through a relatively small incision by being advanced through an IOL insertion cartridge, which causes the IOL to fold. The IOL is typically advanced through the insertion cartridge by a plunger-like device. Unfortunately, as the lens is inserted, the forces that the physician is required to exert on the plunger to move the lens can change drastically (e.g., sudden large decreases) and cause the IOL to suddenly shoot into the eye, which can cause improper IOL placement and damage to eye tissue.
In order to deter uncontrolled plunger advancement rate, some IOL injector systems utilize a metal spring that becomes compressed as the plunger advances. Thus, as the IOL get closer to the injection point into the eye, there is a resistive force from the spring, which can provide a reaction force that opposes force changes from the IOL. Other IOL injector systems may use interference fits between components to influence the rate of plunger advancement.